1. Field of the Invention
This invention concerns a solenoid actuator for use with electromagnetic valves adapted to change the flowing direction of fluid mainly by electromagnetic operation force.
2. Disclosure of Prior Art
A magnetic frame for a solenoid actuator, for example, as shown in FIG. 1 has heretofor been known. The magnetic frame comprises a frame main body 10 having a top plate 11 integrally joined with right and left side plates 12, 13, a bottom plate 14 attached between the lower ends of the side plates 12, 13 by engaging projections 17, 17 provided respectively at the lower ends of the side plates 12, 13 into recesses 18, 19 formed in magnetic flux plates 15, 16 and a magnetic flux plate 20 overlapped with the top plate 11. The thickness for the portion of the top plate 11 overlapped with the magnetic flux plate 20 and that of the bottom plate 14 overlapped with the magnetic flux plates 15, 16 are increased by the overlapping so that the joining areas between each of the central apertures 21, 22 formed in these plates and a stationary core or a movable core to be inserted therein is made equal to or greater than the cross sectional area S of the core. In such a magnetic frame, however, air gaps are present at the abutments 23, 24, 25 between the lower ends of the side plates 12, 13 and the magnetic flux plates 15, 16 and the like that form great magnetic resistance to worsen the performance.